Signatures of Floquet electronic steady states in graphene under continuous-wave mid-infrared irradiation
Yijing Liu, Christopher Yang, Gabriel Gaertner, John Huckabee, A. V. Suslov, Gil Refael, Frederik Nathan, Cyprian Lewandowski, Luis E. F. Foa Torres, Iliya Esin, Paola Barbara, Nikolai G. Kalugin
Abstract
Light-induced phenomena in materials can exhibit exotic behavior that extends beyond equilibrium properties, offering new avenues for understanding and controlling electronic phases. So far, non-equilibrium phenomena in solids have been predominantly explored using femtosecond laser pulses, which generate transient, ultra-fast dynamics. Here, we investigate the steady non-equilibrium regime in graphene induced by a continuous-wave (CW) mid-infrared laser. Our transport measurements reveal signatures of a long-lived Floquet phase, where a non-equilibrium electronic population is stabilized by the interplay between coherent photoexcitation and incoherent phonon cooling. The observation of non-equilibrium steady states using CW lasers stimulates further investigations of low-temperature Floquet phenomena towards Floquet engineering of steady-state phases of matter. Previous investigations of Floquet states in solid state samples have been mostly based on ultrafast light excitations. Here, the authors report evidence of non-equilibrium steady states in graphene under continuous-wave mid-infrared irradiation, consistent with a long-lived Floquet phase physical picture.